Electromagnetic pickup devices are used in conjunction with stringed musical instruments such as electric guitars and basses to convert the vibrations resulting from the movement or “picking” of the strings into electrical signals, for subsequent transmission to amplification devices to produce a desired sound. The pickup is generally positioned under the strings of the instrument on the base surface and the signal transmitted by an electromagnetic pickup is dependent upon the motions of each string.
The most essential components of a pickup are a permanent magnet and a coil of wire. The magnet generates a magnetic field that passes through the pickup coil and also extends into a space occupied by at least one string of the instrument. Vibration of the string changes the reluctance of the magnetic path and creates disturbances in the magnetic field proportional to the string vibration. The changing magnetic field in the pickup coil in turn induces an electrical signal in the coil. From the output of the pickup, a circuit connection is made to an amplifier.
There are several types of pickups with varying coil configurations known in the art. One type of electromagnetic pickup device is a single coil pickup. In a single coil pickup, a single coil portion has a plurality of magnetic pole pieces, with each pole piece associated with a string of the instrument. The pole pieces lie in a place spaced from the common plane of the strings, with each string disposed in a play extending through a space between two adjacent pole pieces, so that a given string at rest is located above and between two adjacent pole pieces.
As a rule, a central design problem of any pickup is that of obtaining both a faithful signal and a good signal to noise ratio. It is well known that the pickup coil, in addition to its desired function of picking up string vibrations, also tends to pick up electrical noise and interference signals from various extraneous sources. Therefore, there is significant value in a pickup that has improved noise rejection of radiated frequencies from extraneous sources while still maintaining response to desirable string vibrations.